1. Field of the Invention.
This invention relates to a method of forming an axle and, more specifically, to such an axle which can be utilized with a central tire inflation system.
2. Description of the Prior Art.
While there have heretofore been a number of methods employed for providing central tire inflation systems, there remains the problem of providing a proper means for providing the inflation air from a fixed source of inflation air on the vehicle to a rotating wheel and tire configuration at the ends of the axles. It has been found that the hub element of such a wheel and tire configuration can be installed on a rigid spindle portion of the axle or axle housing in a manner which will provide a sealed intermediate cavity between the inner and outer bearing elements for the hub. With the intermediate cavity serving as a reservoir for the inflation air for the tire or tires to be mounted thereon, the spindle supporting the hub must be provided passage means for allowing air to be transmitted from the central tire inflation system to the reservoir within the hub.
Although U.S. Pat. No. 3,705,614 discloses a central tire inflation system employing a region intermediate of the bearings of the hub for receipt of the inflation air, the method employed for sealing and transmitting the air is different from that mentioned hereinabove. Nevertheless, the air passages provided in the spindle portion of the axle disclosed therein do adequately and properly allow air from a central tire inflation system to be supplied to this region. However, the type of spindle employed on the axle disclosed in U.S. Pat. No. 3,705,614 is one which includes a large flange portion to be bolted to a flange on a central portion of the axle housing. The bolt holes in the spindle flange can be used as pilot holes when forming the air passages to insure that an air fitting inwardly of the hub is at a predetermined circumferential location to mate with a supply line from the central tire inflation system. While this configuration is acceptable for some axle installations, it is not uncommon for such a bolted flange arrangement to be undesirable and unacceptable because of both weight and space considerations. Accordingly, in such installations, the spindles are initially formed hollow and friction welded or butt welded to a center portion of the axle.
However, in any such axle configuration wherein the spindles are friction welded to a center portion to form the axle, it has been found that the eventual circumferential location of the spindle relative to the center portion is unpredictable. A similar problem of manufacturing control could exist even if the spindles are butt welded to the center portion. Accordingly, in one prior art axle, the inflation air passageways are formed after the spindles are secured to the center portion in order to insure that the inwardly positioned air fitting on the spindle will properly mate with the central tire inflation system. Formation in this manner has required critical drilling of axial passageways and produced stress risers in the axle spindle when drilling the primary radial passageway. As a result, it was not uncommon for axles being formed in this manner to be relatively expensive and subject to quality control problems which could result in some of the axles being rejected as unqualified for use.
Accordingly, there remains a need for providing an axle which is formed by the welding of spindle portions to a center portion and includes passageways therein which can be reasonably formed in a manner which will insure proper mating with a central tire inflation system.